Electrochemical energy storage system, control method and energy storage power station

Abstract

The embodiment of the invention provides an electrochemical energy storage system, a control method and an energy storage power station. The electrochemical energy storage system comprises an energy storage unit, an energy storage converter and a synchronous phase modifier, an alternating current port of the energy storage converter is connected in parallel with a stator alternating current end of the synchronous phase modifier and then is connected to an alternating current bus; the alternating current bus is configured to be connected with a power grid; a first direct current port of the energy storage converter is electrically connected with a rotor excitation end of the synchronous phase modifier; and a second direct current port of the energy storage converter is electrically connected with the energy storage unit. Through coordinated design of the converter and the synchronous camera, power grid disturbance can be responded instantaneously by means of physical inertia of the synchronous phase modifier, and the phase modifier has high over-current capability to deal with a short-circuit fault; meanwhile, the energy storage converter multiplexes the direct current side to excite the phase modifier, the cost is reduced, the adaptability is high, excitation can be actively adjusted, and the reactive response precision of the phase modifier is improved; the two collaboratively construct multi-dimensional support, and the stability of the power grid is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, and in particular to an electrochemical energy storage system, a control method and an energy storage power station. BACKGROUND

[0002] With the transformation of global energy structure to clean and low carbon, new energy power generation technologies such as wind power and photovoltaic power can be developed and applied on a large scale. Although new energy power generation can effectively reduce the consumption of traditional fossil energy and carbon emissions, it is affected by natural conditions (such as wind speed and light intensity), and its output has significant intermittency, volatility and randomness, which greatly increases the difficulty of real-time power balance of the power system and puts forward higher requirements for the frequency modulation, voltage regulation and fault support capacity of the power grid. The electrochemical energy storage system plays an irreplaceable role in the construction of new power system due to its fast response speed, flexible deployment scene, high energy density and precise charge and discharge control.

[0003] However, the current electrochemical energy storage system often adopts a direct connection mode of energy storage units, converters and power grids, although it can realize the storage and release of electric energy, but due to the lack of inertia and reactive power regulation capability, it is difficult to provide effective stability support for the power grid when dealing with power grid frequency mutation, voltage fluctuation and other conditions. SUMMARY

[0004] The electrochemical energy storage system, the control method and the energy storage power station provided by the embodiments of the present application introduce a synchronous phase modifier to make up for the lack of inertia, improve the response speed when the power grid frequency changes, and at the same time, through the cooperation of the energy storage converter and the synchronous phase modifier, enhance the reactive power support capability when the power grid fails, guarantee the stable operation of the system, and adapt to the demand of high proportion of new energy power grid.

[0005] In a first aspect, the embodiments of the present application provide an electrochemical energy storage system, comprising: an energy storage unit, an energy storage converter and a synchronous phase modifier; the AC port of the energy storage converter and the stator AC port of the synchronous phase modifier are connected in parallel to an AC bus, and the AC bus is configured to be connected with a power grid; the first DC port of the energy storage converter is electrically connected with the rotor excitation end of the synchronous phase modifier for excitation; and the second DC port of the energy storage converter is electrically connected with the energy storage unit to realize the charge and discharge of the energy storage unit.

[0006] In a possible implementation, the energy storage converter is configured to operate in a grid-forming mode.

[0007] In a possible implementation, the energy storage converter adopts virtual synchronous machine control.

[0008] In a possible implementation, the energy storage converter has a virtual inertia regulation function.

[0009] In a possible implementation, the energy storage converter is further configured to calculate the output voltage of the first DC port based on a frequency fluctuation parameter of the power grid.

[0010] In a possible implementation, the energy storage converter is further configured to adjust at least one of the following parameters: virtual damping, AC voltage, and field DC voltage.

[0011] In a possible implementation, the energy storage converter is further configured to calculate a target field voltage of the synchronous condenser based on a voltage fault parameter of the power grid; and adjust the output voltage of the first DC port according to the target field voltage.

[0012] In a possible implementation, each phase bridge arm of the energy storage converter adopts a cascaded topology of multiple sub-modules, the AC sides of the multiple sub-modules are connected in series, and the DC sides are connected to the energy storage unit.

[0013] In a possible implementation, the energy storage converter is a modular multilevel converter or a modular multilevel matrix converter.

[0014] In a possible implementation, the sub-module comprises an AC-DC conversion module, a first DC converter, and a second DC converter connected in sequence.

[0015] In a possible implementation, the third DC bus is connected to a second DC bus through the second DC converter, the second DC bus is connected to the energy storage unit, the energy storage unit is connected to the first DC bus through the first DC converter, and the first DC bus is connected to the DC side of the AC-DC conversion module.

[0016] In a possible implementation, the first DC converter and / or the second DC converter is an isolated DC converter.

[0017] In a possible implementation, the second DC buses among the multiple sub-modules in each phase bridge arm are connected in parallel.

[0018] In a possible implementation, the third DC buses among the multiple sub-modules in each phase bridge arm are connected in parallel.

[0019] In a possible implementation, different sub-modules in the same bridge arm are connected in series through the second DC bus.

[0020] In a possible implementation, different sub-modules in the same bridge arm are connected in series through the third DC bus.

[0021] In a second aspect, the embodiments of the present application provide a control method of an electrochemical energy storage system, applied to the electrochemical energy storage system provided in the first aspect of the present application. The method comprises: controlling the first direct current port of the energy storage converter to output a specified voltage; and electrically connecting the electrochemical energy storage system to the power grid if the rotor speed of the synchronous condenser matches the voltage frequency of the power grid and the phase difference between the voltage phase of the alternating current bus and the voltage phase of the power grid is less than or equal to a preset value. In a possible implementation, the method further comprises: if the voltage parameter output by the stator side of the synchronous generator does not match the voltage parameter of the power grid, adjusting the output of the second alternating current port of the energy storage converter until the voltage parameter output by the stator side of the synchronous generator matches the voltage parameter of the power grid.

[0022] In a possible implementation, the method further comprises: if the voltage parameter of the first alternating current port does not match the voltage parameter of the power grid, adjusting the output of the first alternating current port of the energy storage converter until the voltage parameter of the first alternating current port matches the voltage parameter of the power grid.

[0023] In a third aspect, the embodiments of the present application provide an energy storage power station, comprising a charging pile and the electrochemical energy storage system provided in the first aspect of the present application.

[0024] The electrochemical energy storage system, the control method and the energy storage power station provided by the embodiments of the present application have the following advantages. The energy storage converter and the synchronous condenser are connected in parallel to the alternating current bus and then connected to the power grid, so that the transformer between the two and the high-voltage bus is omitted, the electrical distance is reduced, and the power grid fluctuation can be responded more quickly. The energy storage converter is used to excite the rotor of the condenser, the DC side voltage is reused, the dedicated excitation equipment is omitted to save cost, and the DC side and the AC side of the converter are decoupled through the cascade topology, so that the voltage adjustable range is large and the condenser of various specifications can be adapted. The excitation is dynamically adjusted to improve the reactive power regulation accuracy and response speed of the condenser. The energy storage converter can also provide virtual inertia to make up for the small inertia of the condenser. The synchronous condenser responds to the power grid disturbance instantaneously by virtue of physical inertia and has large overcurrent capacity to cope with short-circuit faults, and the power grid stability is enhanced in cooperation with the energy storage converter. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0026] Figure 1 FIG. 1 is a structural schematic diagram of an energy storage power station provided by the present application;

[0027] Figure 2 FIG. 2 is a structural schematic diagram of an electrochemical energy storage system 20 provided by the present application;

[0028] Figure 3 FIG. 3 is a structural schematic diagram of an energy storage converter provided by the present application; Figure 2Simulation waveform diagram of the electrochemical energy storage system 20 when the grid frequency changes;

[0029] Figure 4A For the present application Figure 2 Simulation waveform diagram of the electrochemical energy storage system 20 when the grid voltage fails;

[0030] Figure 4B For the present application Figure 2 Simulation waveform diagram of the electrochemical energy storage system 20 when the grid voltage fails;

[0031] Figure 5 Structural schematic diagram of another electrochemical energy storage system 20 provided for the present application;

[0032] Figure 6 Structural schematic diagram of another electrochemical energy storage system 20 provided for the present application;

[0033] Figure 7 Structural schematic diagram of another electrochemical energy storage system 20 provided for the present application;

[0034] Figure 8 For the present application Figure 2 Schematic diagram of the first cascade topology of the energy storage converter 220 shown in the present application;

[0035] Figure 9 For the present application Figure 2 Schematic diagram of the second cascade topology of the energy storage converter 220 shown in the present application;

[0036] Figure 10 For the present application Figure 2 Schematic diagram of the third cascade topology of the energy storage converter 220 shown in the present application;

[0037] Figure 11 Topological schematic diagram of the first sub-module and DC bus provided for the embodiments of the present application;

[0038] Figure 12 Topological schematic diagram of the second sub-module and DC bus provided for the embodiments of the present application;

[0039] Figure 13 Topological schematic diagram of the third sub-module and DC bus provided for the embodiments of the present application;

[0040] Figure 14 Topological schematic diagram of the fourth sub-module and DC bus provided for the embodiments of the present application;

[0041] Figure 15 Topological schematic diagram of the fifth sub-module and DC bus provided for the embodiments of the present application;

[0042] Figure 16A sixth sub-module and DC bus topology schematic diagram provided by the embodiment of the application;

[0043] Figure 17 A seventh sub-module and DC bus topology schematic diagram provided by the embodiment of the application;

[0044] Figure 18 A structure schematic diagram of another energy storage power station provided by the application;

[0045] Figure 19 A flowchart of the control method of the electrochemical energy storage system provided by the application.

[0046] Reference signs:

[0047] 20 - electrochemical energy storage system;

[0048] 210 - energy storage unit; 220 - energy storage converter; 230 - synchronous condenser;

[0049] T1 - first transformer; T2 - second transformer;

[0050] OUT1 - first DC port; OUT2 - second DC port; OUT3 - AC port.

[0051] Through the above drawings, the specific embodiments of the application have been shown, and more detailed descriptions will be given hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of the application by any means, but to illustrate the concept of the application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0052] The exemplary embodiments will be described in detail herein with reference to the accompanying drawings. In the following description, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments are not meant to represent all implementations consistent with the application. Rather, they are merely examples of apparatus and methods consistent with some aspects of the application as detailed in the appended claims.

[0053] First, the terms involved in the application are explained:

[0054] MMC (Modular Multilevel Converter): a power electronic converter composed of a plurality of sub-modules in cascade, which realizes smooth regulation of voltage and current through ordered switching of sub-modules, and has the characteristics of high output waveform quality, low harmonic content, large power capacity, etc.

[0055] Sub-module: the basic functional unit constituting the bridge arm of the converter.

[0056] M 3 C-type energy storage converter: refers to a modular multilevel matrix converter (MMC). Its topology consists of three MMC bridge arms connected in staggered parallel at both ends. It has multiple AC and DC output terminals. Each phase bridge arm adopts a multi-submodule cascaded topology, with the submodules connected in series on the AC side and connected to the energy storage unit and DC conversion module on the DC side. The output terminals are bidirectional input / output ports, also known as ports.

[0057] RoCoF stands for Rate of Change of Frequency, used to measure how quickly the power grid frequency changes, measured in Hz / s. The larger the system inertia, the smaller the RoCoF, and the slower the frequency drops, thus reducing power grid stability problems caused by sudden frequency drops.

[0058] The power grid experiences peak and off-peak electricity demand. By integrating energy storage systems into the grid, the storage and release of electrical energy can be achieved. During off-peak hours, the energy storage system absorbs and stores excess electrical energy from the grid to avoid energy waste. During peak hours, the energy storage system releases the stored electrical energy to supplement the grid's electricity demand and alleviate the peak-shaving pressure on the generation side.

[0059] Figure 1 A structural schematic diagram of an energy storage power station provided in this application is shown below. Figure 1 As shown, an energy storage power station includes a DC bus, an AC bus, and various energy-related equipment, such as wind power generation equipment, photovoltaic power generation equipment, and thermal power generation equipment. Energy exchange between the DC bus and the AC bus is achieved through an energy storage system. The photovoltaic power generation equipment is connected to the DC bus, converting solar energy into DC electricity which is then input into the DC bus; the energy storage equipment is also connected to the DC bus, enabling the storage and release of electrical energy on the DC side. On the AC side, photovoltaic / wind power generation equipment, as well as thermal / hydropower / nuclear power generation equipment, are all connected to the AC bus, providing power to it. The AC bus connects to the power grid, enabling energy exchange with the external power grid, and also supplies power to local loads.

[0060] Meanwhile, the energy storage system can flexibly adjust energy between the DC bus and the AC bus, ensuring efficient energy distribution and stable supply for the entire energy storage power station. Different types of energy storage systems are aggregated through the AC bus within the station and then connected to the power grid via step-up transformers, grid-connected circuit breakers, etc., and can also supply energy to local loads such as charging piles and industrial loads within the station.

[0061] The traditional electrochemical energy storage system has a multi-loop control strategy when realizing DC-AC energy conversion through a converter, which introduces a response delay of tens of milliseconds and easily causes control parameter coupling oscillation under dynamic conditions, thereby inducing power grid oscillation events. At the same time, the converter only has an overcurrent capacity of 1.2-1.5 times the rated current, and when a short-circuit fault occurs in the power grid, the current limiting mechanism of the converter will trigger fast off-grid protection, forming a chain reaction, resulting in the loss of important power support for the power grid. Especially in the power grid where the proportion of new energy is relatively high, this off-grid may cause systemic risks such as frequency drop and voltage collapse, and aggravate the vulnerability of the power grid.

[0062] To solve the foregoing problems, the inventors of the present application found that a synchronous condenser can be added to the electrochemical energy storage system. However, the synchronous condenser has a small inertia and cannot provide sufficient support, and the cost of the condenser system is relatively high.

[0063] To overcome the problem of the cost of the condenser, the DC side voltage of the energy storage converter can be used for condenser excitation to avoid using a dedicated excitation cost. However, the DC side voltage cannot be freely adjusted due to the battery voltage clamping, and the adjustment range of the DC side voltage of the converter is also limited by the AC measurement voltage amplitude and the device withstand voltage, resulting in a small adjustment range and difficulty in adapting to general condensers. At the same time, the AC side voltage of the energy storage converter is low, for example, less than 1 kV, which needs to be connected to the grid through a step-up transformer, resulting in a decrease in system efficiency and an increase in the electrical distance between the device and the power grid, which delays the response speed to power grid fluctuations.

[0064] Based on this, the present application provides an electrochemical energy storage system. On the basis of introducing a synchronous condenser to utilize its physical inertia to realize instantaneous response to power grid disturbances and rely on large overcurrent capacity to cope with short-circuit faults, the energy storage converter adopts a high-voltage cascade topology to realize the decoupling of the DC side and the AC side voltage, get rid of the battery voltage clamping, and flexibly adjust the DC side voltage to adapt to various specifications of condensers. At the same time, the AC ports of the energy storage converter and the condenser are directly connected in parallel to the high-voltage bus, eliminating the step-up transformer, reducing energy loss, shortening the electrical distance, and responding more quickly to power grid fluctuations, which not only solves the problem of limited excitation voltage adjustment but also improves the system efficiency and response speed.

[0065] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0066] Figure 2 A structural schematic diagram of an electrochemical energy storage system 20 provided by the present application is shown in FIG. 1. Figure 2As shown, the electrochemical energy storage system 20 comprises an energy storage unit 210, an energy storage converter 220 and a synchronous compensator 230.

[0067] The energy storage converter 220 has an alternating current port and multiple direct current output terminals, and the subsequent first direct current terminal OUT1 and the second direct current terminal OUT2 can be any direct current output terminal among the multiple direct current output terminals.

[0068] The alternating current port OUT3 of the energy storage converter 220 is connected in parallel with the stator side alternating current terminal of the synchronous compensator 230 and is connected to an alternating current bus configured to be connected to a power grid; the first direct current terminal OUT1 of the energy storage converter 220 is electrically connected to the rotor excitation terminal of the synchronous compensator 230 for excitation; and the second direct current terminal OUT2 of the energy storage converter 220 is electrically connected to the energy storage unit 210 to realize charging and discharging of the energy storage unit 210.

[0069] The energy storage unit 210 is used for storing and releasing electric energy and can be composed of multiple battery clusters in parallel, which can be lithium battery clusters, sodium batteries, vanadium flow battery stacks, etc. It can also contain a battery management system for monitoring the state of single batteries, such as voltage, temperature, etc., to avoid overcharging, overdischarging, excessive temperature, etc.

[0070] The energy storage converter 220 is used to realize the conversion of electric energy forms, specifically the bidirectional conversion of direct current and alternating current, and is also used for power regulation, frequency conversion and speed regulation, etc.

[0071] The energy storage converter 220 has multiple independent direct current output terminals and an alternating current port. Modular multilevel matrix converter (M3C) or modular multilevel converter (MMC) can be used, which contains a cascaded topology of submodules, such as full-bridge H-bridge submodules. By using cascaded topology, the voltage decoupling between the direct current side and the alternating current side of the energy storage converter 220 is realized, so that the regulation of the alternating current side voltage can be realized by controlling the internal submodules without relying on the voltage change of the direct current side.

[0072] The rotor excitation terminal of the synchronous compensator 230 refers to the port of the rotor winding of the synchronous compensator 230 connected to the external excitation device, through which the excitation current is connected to generate a rotating magnetic field to provide magnetic field excitation for the operation of the synchronous compensator 230. The stator side alternating current terminal of the synchronous compensator 230 is the port of the stator winding of the synchronous compensator 230 connected to the external alternating current circuit, through which the synchronous compensator 230 can be electrically connected to the alternating current bus and the alternating current port OUT3 of the energy storage converter 220.

[0073] The alternating current bus is used to collect the electric energy output by each component as a public interface for the connection between the electrochemical energy storage system 20 and the external power grid, and also supplies power to local loads, which can be composed of copper bars or high-voltage cables and has the characteristics of carrying large current and low impedance.

[0074] At the low electricity consumption valley of the power grid, the control of the power grid energy flow to the energy storage unit 210 of the electrochemical energy storage system 20 realizes the battery charging. At the peak of the power grid electricity consumption, the energy flow of the energy storage unit 210 is controlled to the power grid to realize the battery discharging.

[0075] In the discharging process, the direct current output by the energy storage unit 210 is inverted into alternating current by the energy storage converter 220, and one way is connected to the alternating current bus through the parallel connection of the alternating current port OUT3 and the stator side alternating current end of the synchronous phase modifier 230 to supply power to the power grid.

[0076] In the charging process, the power of the power grid is divided into two ways through the alternating current bus into the energy storage converter 220: one way is transmitted through the stator side alternating current end of the synchronous phase modifier 230 to drive its operation and convert into mechanical energy, and then rectified into direct current by the energy storage converter 220; the other way is directly connected to the energy storage converter 220 through the alternating current port to be rectified into direct current, and the two ways of direct current jointly charge the energy storage unit 210 to realize energy storage.

[0077] Optionally, the energy storage converter 220 is configured to operate in a grid-forming mode.

[0078] In the grid-forming mode, the energy storage converter 220 simulates the voltage regulation, frequency response and inertia characteristics of the synchronous motor, and can autonomously build and maintain the voltage and frequency of the power grid to support the stable operation of the power grid and improve the response ability of the system to the power grid fluctuations.

[0079] In some embodiments, the energy storage converter 220 can also be configured to operate in a grid-following mode.

[0080] In the grid-following mode, the operating state of the energy storage converter 220 depends on the voltage and frequency signals of the external power grid, and the voltage and frequency of its output follow the changes of the voltage and frequency of the power grid. Specifically, when in the discharging process, the direct current output by the energy storage unit 210 is inverted into alternating current with the same frequency and phase as the power grid by the energy storage converter 220, and is connected to the alternating current bus through the parallel connection of the alternating current port and the stator side alternating current end of the synchronous phase modifier 230, at this time the converter adjusts its output according to the voltage and frequency of the power grid to ensure synchronization with the power grid and deliver power to the power grid.

[0081] Optionally, the alternating current bus is connected to the power grid through a grid-connected circuit breaker.

[0082] The grid-connected circuit breaker is a high-voltage switching element between the alternating current bus and the power grid, which has two action modes of normal on-off and fault tripping.

[0083] When the power grid needs power support, for example, at the peak of electricity consumption, the grid-connected circuit breaker is closed, and the electrochemical energy storage system 20 delivers power to the power grid. When the power grid does not need the electrochemical energy storage system 20 to operate in grid-connected mode, the grid-connected circuit breaker is opened.

[0084] When a short-circuit fault occurs in the power grid, the grid-connected circuit breaker remains closed, ensuring that the electrochemical energy storage system 20 outputs reactive power to the power grid.

[0085] The on-off of the grid-connected circuit breaker can be remotely controlled, and the grid-connected or off-grid state of the electrochemical energy storage system 20 can be flexibly scheduled.

[0086] When a fault occurs on the electrochemical energy storage system 20 side, the connection between the system and the power grid can be quickly cut off by the fault tripping of the grid-connected circuit breaker, preventing the fault from spreading to the power grid and ensuring the safe and stable operation of the power grid.

[0087] As the "gateway" between the AC bus and the power grid, the grid-connected circuit breaker realizes safe and controllable interaction between the system and the power grid through flexible on-off control, which not only ensures the safety of the equipment and the power grid during a fault, but also supports flexible scheduling and scenario switching during normal operation.

[0088] Optionally, a filter reactor is connected in series between the AC bus and the grid-connected circuit breaker.

[0089] When the energy storage converter 220 performs high-frequency switching operations, high-order harmonics are generated, so a filter reactor is introduced to form an impedance barrier for high-order harmonics, which can significantly attenuate high-order harmonic currents and make the current waveform flowing into the power grid closer to a sine wave.

[0090] In a power grid with a high proportion of new energy and energy storage, the fast response characteristics of the converter may resonate with the inductive / capacitive load of the power grid, causing periodic fluctuations in voltage or current amplitude and threatening system stability. The filter reactor can adjust the inductance parameter to change the resonance frequency of the system, so that the resonance point deviates from the normal working frequency range, thereby suppressing the generation of resonance.

[0091] The electrochemical energy storage system 20 provided in the embodiment connects the energy storage converter and the synchronous condenser AC port in parallel to access the AC bus and reconnect the power grid, eliminating the transformer between the two and the high-voltage bus, reducing the electrical distance, and responding more quickly to power grid fluctuations; the energy storage converter is used to excite the rotor of the condenser, the DC side voltage is reused, and dedicated excitation equipment is eliminated to save costs, and the DC side and AC side voltages of the converter are decoupled through the cascaded topology, the voltage adjustment range is large, and various specifications of condensers are adapted; the excitation is dynamically adjusted to improve the reactive power regulation accuracy and response speed of the condenser; the energy storage converter can also provide virtual inertia to compensate for the small inertia of the condenser; the synchronous condenser responds to power grid disturbances instantaneously due to physical inertia, and has a large current capacity to deal with short-circuit faults, which, together with the energy storage converter, enhances the stability of the power grid.

[0092] Optionally, the energy storage converter 220 adopts virtual synchronous machine control.

[0093] The virtual synchronous machine control is specifically to simulate the rotor inertia, damping characteristics and excitation regulation of the synchronous generator through a control algorithm, so that the energy storage converter 220 has frequency and voltage response capabilities similar to those of a synchronous machine.

[0094] Optionally, the energy storage converter 220 has a virtual inertia regulation function.

[0095] The virtual inertia regulation function refers to dynamically simulating the rotor inertia characteristics of a synchronous generator through a control algorithm, which can adjust the output power in real time according to the change of the grid frequency to suppress the frequency fluctuation of the grid.

[0096] The synchronous condenser 230 is a synchronous machine modified from a generator, which removes the rotating parts of the original prime mover (such as a steam turbine or a water turbine) and only retains the generator part, so the moment of inertia is greatly reduced, usually only 10% - 15% of the conventional generator set (such as a thermal power generator set) of the same capacity. At the same time, the synchronous condenser 230 does not carry mechanical load when it operates, and its main function is to provide reactive power support, and its rotor design focuses more on electrical performance optimization rather than mechanical kinetic energy storage, further limiting its inertia level.

[0097] Based on this, the energy storage converter 220 can compensate for the lack of inertia of the synchronous condenser 230 by using a virtual synchronous machine control strategy. The energy storage converter 220 can simulate the inertia characteristics of a synchronous machine and release or absorb energy through a control algorithm when the grid frequency fluctuates, providing virtual inertia support, which cooperates with the physical inertia of the synchronous condenser 230 to enhance the anti-disturbance capability of the system and improve the stability of the grid.

[0098] Optionally, the energy storage converter 220 is further configured to: calculate the output voltage of the first DC port OUT1 based on a frequency fluctuation parameter of the grid; and / or, calculate a target excitation voltage of the synchronous condenser based on a voltage fault parameter of the grid; and adjust the output voltage of the first DC port OUT1 according to the target excitation voltage.

[0099] Optionally, when performing virtual inertia regulation, the energy storage converter 220 is configured to: detect a frequency fluctuation parameter of the grid; and calculate the output voltage of the first DC port OUT1 based on the frequency fluctuation parameter and a virtual synchronous machine control algorithm.

[0100] The frequency fluctuation parameter is used to represent the change of the frequency and can include the difference between the frequency and the rated value, the frequency change rate, etc.

[0101] When the virtual inertia adjustment is performed, the energy storage converter 220 monitors the frequency fluctuation parameter of the power grid in real time, and based on the monitored frequency fluctuation parameter, in combination with the virtual synchronous machine control algorithm, simulates the inertia response of the synchronous generator to determine the virtual inertia, and then based on the virtual inertia, calculates the output voltage of the first DC port OUT1, i.e., the excitation DC voltage of the synchronous compensator 230.

[0102] By real-time monitoring of the frequency change of the power grid, the excitation DC voltage of the synchronous compensator 230 is adjusted, the virtual inertia is supplemented, the disadvantage of low physical inertia of the synchronous compensator 230 is overcome, the power grid frequency fluctuation is quickly responded to, the frequency change is suppressed, and the power grid stability is improved.

[0103] In addition to the virtual inertia adjustment, the energy storage converter 220 can also have the adjustment function of the virtual damping, AC voltage, and excitation DC voltage parameters.

[0104] Optionally, the energy storage converter 220 is also configured to adjust at least one of the following parameters: virtual damping, AC voltage, and excitation DC voltage.

[0105] Among them, the virtual damping is a damping characteristic parameter simulated by a control algorithm to suppress the frequency or voltage fluctuation and vibration phenomenon of the electrochemical energy storage system 20. The AC voltage is the voltage of the AC port OUT3 of the energy storage converter 220, the AC bus, and the connection point of the synchronous compensator 230. The excitation DC voltage is the voltage provided by the first DC port OUT1 of the energy storage converter 220 to the rotor excitation end of the synchronous compensator 230 to control the excitation current and reactive power output capability of the synchronous compensator 230.

[0106] For the virtual damping, when the frequency or voltage fluctuation of the electrochemical energy storage system 20 is detected to be large and the oscillation is obvious, the virtual damping coefficient can be increased to enhance the energy dissipation effect to quickly suppress the oscillation; then, when the system tends to be stable, the virtual damping system is reduced to avoid excessive suppression leading to slow response.

[0107] For the AC voltage, the amplitude, phase, and frequency of the AC voltage can be monitored in real time, compared with the rated value, and based on the comparison result, a deviation signal is generated, and based on the deviation signal, the AC voltage is adjusted.

[0108] For the excitation DC voltage, the voltage of the first DC port OUT1 of the energy storage converter 220 can be adjusted according to the grid voltage state or the received demand instruction, so as to adjust the excitation DC voltage. When the grid voltage is low, the excitation DC voltage is increased to increase the excitation current and enhance the magnetic field of the synchronous compensator 230 to provide more power to the power grid; when the grid voltage is high, the excitation DC voltage is reduced to reduce the excitation current, and the synchronous compensator 230 reduces the power output or absorbs power.

[0109] Through multi-dimensional parameter adjustment, the system performance is further optimized, the virtual damping adjustment suppresses the oscillation after the fluctuation, the alternating current voltage adjustment ensures the stability of the output voltage, and the excitation direct current voltage adjustment optimizes the reactive power support capability of the synchronous condenser, and the three work together to comprehensively improve the dynamic stability, adaptability to the power grid and operation reliability of the electrochemical energy storage system under different working conditions.

[0110] Due to the access of the synchronous condenser 230 and the virtual synchronous machine control of the energy storage converter 220, the electrochemical energy storage system 20 will have a large current response to voltage disturbance changes, the equivalent short-circuit capacity of the system increases, and the short-circuit ratio increases, which can effectively suppress the fluctuation of the alternating current voltage.

[0111] When the grid voltage rises, the synchronous condenser 230 absorbs a large amount of reactive power, and when the grid voltage drops, the synchronous condenser 230 outputs a large amount of reactive power to avoid excessive voltage fluctuation.

[0112] When a short circuit occurs in the power grid, the excitation winding of the synchronous condenser 230 will maintain the magnetic field strength in a short time due to the flux linkage conservation characteristic, release the inductive reactive power, compensate for the reactive power deficiency at the fault point, and delay the voltage drop speed.

[0113] Further, the excitation direct current voltage of the synchronous condenser 230 can be dynamically adjusted through active control of the energy storage converter 220.

[0114] Optionally, when adjusting the excitation direct current voltage, the energy storage converter 220 is configured to: detect a voltage fault parameter of the power grid; calculate a target excitation voltage of the synchronous condenser 230 based on the voltage fault parameter; and adjust the output voltage of the first direct current port OUT1 according to the target excitation voltage.

[0115] The voltage fault parameter is an index reflecting the voltage abnormal state when the voltage drop fault caused by the short circuit of the power grid, the sudden change of large-capacity load, etc., which can be voltage change rate, voltage drop amplitude, fault duration, fault type, etc.

[0116] The energy storage converter 220 can use any control strategy to calculate the target excitation voltage, such as a proportional-integral control strategy.

[0117] After determining the target excitation voltage, the energy storage converter 220 adjusts the actual output voltage of its first direct current port OUT1 by controlling the conduction or blocking of the internal power electronic switch, so that the actual output voltage approaches the target excitation voltage.

[0118] When a short circuit or other fault in the power grid causes a voltage drop, the energy storage converter 220 first detects the grid voltage fault parameters in real time and quickly calculates the target excitation voltage suitable for the current fault condition based on these parameters. Subsequently, by adjusting the output voltage of the first DC port OUT1, it provides a stronger excitation current to the excitation winding of the synchronous condenser 230, thereby increasing the reactive power output of the synchronous condenser 230, extending the duration of reactive power support, and providing more time for fault isolation and grid restoration.

[0119] Figure 3 For this application Figure 2 The simulation waveform diagram of the electrochemical energy storage system 20 under grid frequency changes is shown below. Figure 3 As shown, when the power grid frequency changes, the synchronous condenser 230 can briefly generate or absorb active power without delay due to physical inertia, so as to suppress the frequency change. Figure 3 Taking a linear decrease in grid frequency starting at time t0 as an example, the synchronous condenser 230 responds without delay, adding a small inertia power on top of the original power to suppress the frequency decrease. The energy storage converter 220 needs to first input the grid voltage, calculate the target voltage value using a virtual synchronous machine control algorithm, and output this target value through the first DC port OUT1 by controlling the internal switching diodes. Therefore, the entire process involves a certain delay. Thus, when the grid frequency fluctuates, for example, decreases, the energy storage converter 220 responds with a delay, adding a large inertia power on top of the original power to further suppress the frequency decrease.

[0120] Figure 4A and Figure 4B All of these are from this application. Figure 2 The simulation waveform diagram of the electrochemical energy storage system 20 under grid voltage fault is shown below. Figure 4A For the case where the energy storage converter 220 does not perform excitation DC voltage regulation, Figure 4B This refers to the case where the excitation DC voltage of the energy storage converter 220 is regulated. For example... Figure 4A and Figure 4B As shown, during a grid voltage fault, the voltage drops, and the corresponding currents of the synchronous condenser and the energy storage converter 220 are as follows: Figure 4A and Figure 4B As shown.

[0121] Because the energy storage converter 220 can regulate the excitation DC voltage, when a voltage fault occurs in the power grid, it can actively regulate the excitation of the synchronous condenser by controlling the output of a strong or weak excitation voltage. According to the characteristics of the synchronous motor, changes in excitation directly lead to changes in the amplitude of the internal electromotive force (EMF) of the condenser. Changes in the difference between the internal EMF and the grid voltage affect the reactive current output of the synchronous motor. This active excitation regulation allows the condenser to output a higher reactive current support during faults, thereby enhancing its reactive power support capability for the power grid, helping to maintain grid voltage stability, and mitigating voltage problems caused by faults. (Comparison) Figure 4A and Figure 4B It can be seen that by actively adjusting the excitation DC voltage through the energy storage converter 220, the voltage drop of the power grid is alleviated.

[0122] The electrochemical energy storage system may also include a conventional converter. This conventional converter can be any existing converter, complementing the multi-AC port energy storage converter 220. The conventional converter may have only one AC port, which can be directly connected to the AC bus after connecting a series switching element.

[0123] The conventional converter can be an existing converter in the energy storage system. The energy storage converter 220 is superimposed on the existing structure of the energy storage power station to introduce the electrochemical energy storage system 20 into the energy storage power station, thus eliminating the need to modify the conventional converter.

[0124] The DC output terminals of the conventional converter and the energy storage converter 220 can be connected to different energy storage units respectively.

[0125] Figure 5 A schematic diagram of another electrochemical energy storage system 20 provided in this application, and... Figure 2 Compared to the electrochemical energy storage system 20 shown, in this embodiment, there are two converters, including a first converter and a second converter. The first converter is the aforementioned energy storage converter 220, and the second converter is any other type of converter. The energy storage unit is composed of multiple battery clusters connected in parallel, such as battery clusters 11 to 1n, and battery clusters 21 to 2m.

[0126] Each converter can correspond to one energy storage unit, or one energy storage unit can be connected to multiple converters.

[0127] The second DC port OUT2 of the first converter is connected with the battery cluster 11 to the battery cluster 1n, and the DC output end of the second converter is connected with the battery cluster 21 to the battery cluster 2m, wherein m and n are both integers greater than 1. The first DC port OUT1 and the AC port OUT3 of the first converter are connected in the manner provided in the foregoing embodiments. A circuit breaker is further arranged in each branch. The AC bus is connected to the power grid in sequence through a filter reactor and a grid-connected circuit breaker.

[0128] Optionally, the AC port OUT3 of the energy storage converter 220 is connected to the AC bus through a first step-up transformer T1, and the stator AC end of the synchronous compensator 230 is connected to the AC bus through a second step-up transformer T2.

[0129] By being connected to the AC bus through transformers respectively, different transformation ratios can be set to adapt to the voltage characteristics of the energy storage converter 220 and the synchronous compensator 230, which improves flexibility and facilitates expansion.

[0130] Figure 6 Another structural schematic diagram of an electrochemical energy storage system 20 provided in the present application is shown in FIG. 6. Figure 6 As shown in the figure, in the present embodiment, the electrochemical energy storage system 20 further comprises transformers, circuit breakers and contactors.

[0131] The AC port OUT3 of the energy storage converter 220 is connected to the AC bus through a first transformer T1, and the stator AC end of the synchronous compensator 230 is connected to the AC bus through a second transformer T2. Both ends of the first transformer T1 are connected in series with circuit breakers, and both ends of the second transformer T2 are also connected in series with circuit breakers. Power is collected through the AC bus and finally connected to the power grid.

[0132] The first DC port OUT1 of the energy storage converter 220 is connected to the rotor excitation end of the synchronous compensator 230 through a DC converter DC / DC and a contactor for excitation.

[0133] The DC bus shown in the figure can be a subsequent first DC bus, a second DC bus, a third DC bus or an MMC DC bus.

[0134] Optionally, the AC port OUT3 of the energy storage converter 220 is connected to the AC bus through a step-up transformer in parallel with the stator AC end of the synchronous compensator 230.

[0135] By sharing one step-up transformer, the number of devices is reduced, the cost and land occupation of the devices are reduced, and by unified control, the power distribution deviation is reduced.

[0136] Figure 7 Another structural schematic diagram of an electrochemical energy storage system 20 provided in the present application is shown in FIG. 6. Figure 7As shown, in the present embodiment, the electrochemical energy storage system 20 also includes a transformer, a circuit breaker and a contactor. Compared with the prior art, the present embodiment uses only one transformer to realize power collection. Figure 6 The present embodiment realizes power collection through the transformer.

[0137] The AC port OUT3 of the energy storage converter 220 is connected in parallel with the branch formed by the stator AC side of the synchronous condenser 230 and the circuit breaker, and is connected to the AC bus through the transformer. Power collection is realized through the AC bus, and is finally connected to the power grid.

[0138] Optionally, each phase bridge arm of the energy storage converter 220 adopts a cascade topology of multiple sub-modules, and the AC sides of the multiple sub-modules are connected in series, and the DC sides are connected to the energy storage unit 210.

[0139] Each phase bridge arm of the energy storage converter 220 is formed by connecting multiple functionally independent sub-modules in series according to a certain rule. Taking a three-phase converter as an example, each phase is composed of a plurality of sub-modules connected in series to form a bridge arm, and the three-phase bridge arms are connected in star or delta to form a complete main circuit of the converter.

[0140] For example, the energy storage converter 220 can be a cascade H-bridge converter.

[0141] Each sub-module contains power switching devices, capacitors and drive protection circuits, and can independently realize the control of access or exit of the main circuit.

[0142] Through the cascade topology and independent control of multiple sub-modules, flexible expansion of voltage levels is realized.

[0143] Optionally, the bridge arm of the energy storage converter 220 adopts star or double-star connection.

[0144] Optionally, the energy storage converter 220 is a modular multilevel converter or a modular multilevel matrix converter.

[0145] Figure 8 For the present application Figure 2 The schematic diagram of the first cascade topology of the energy storage converter 220 is shown in FIG. 1. Figure 8 As shown, the bridge arm of the energy storage converter 220 is connected in double-star, forming an MMC DC bus and an AC interface, i.e. an AC port OUT3.

[0146] Figure 9 For the present application Figure 2 The schematic diagram of the second cascade topology of the energy storage converter 220 is shown in FIG. 2. Figure 9 As shown, the bridge arm of the energy storage converter 220 is connected in star, forming a three-phase AC interface.

[0147] Figure 10 For the present applicationFigure 2 A schematic diagram of a third cascaded topology of the energy storage converter 220 is shown in FIG. 3B. Figure 10 As shown, the bridge arms of the energy storage converter 220 are connected by a double star type connection to form an MMC DC bus and a three-phase AC interface. Meanwhile, a string of sub-modules is connected to the MMC DC bus.

[0148] Alternatively, the bridge arms of the energy storage converter 220 are connected by a double star type connection to form an MMC DC bus; and the MMC DC bus selectively has a string of sub-modules connected thereto, the string of sub-modules being formed by a plurality of sub-modules connected in series.

[0149] The selective connection means that the string of sub-modules can be connected to the MMC DC bus according to operating requirements, changes in working conditions, or fault detection results, etc.

[0150] The flexible connection of the string of sub-modules further improves the voltage regulation range to adapt to the requirements of the DC side voltage under different working conditions.

[0151] Alternatively, the sub-module comprises a secondary connected AC / DC conversion module, a first DC / DC converter, and a second DC / DC converter.

[0152] The first DC / DC converter and the second DC / DC converter can be a Buck DC / DC converter, a Boost DC / DC converter, or an isolated DC / DC converter.

[0153] Alternatively, the first DC / DC converter and / or the second DC / DC converter is an isolated DC / DC converter.

[0154] Through the isolated DC / DC converter, the function of electrical isolation is achieved on the basis of DC power conversion, effectively suppressing interference signals in the circuit, and also blocking the propagation of faults to some extent, thereby improving the safety and reliability of the system.

[0155] Illustratively, the isolated DC / DC converter can be a push-pull isolated DC / DC converter, a half-bridge isolated DC / DC converter, or other isolated DC / DC converters.

[0156] For the energy storage converter 220 using the topology shown in FIG. 1A, FIG. 1B, or FIG. 1C, the structure of the internal sub-module is shown in FIG. 2A. Figure 8 Figure 9 Figure 10 Figures 11 to 17

[0157] The first DC port OUT1 and the second DC port OUT2 can be associated with any of the first DC bus, the second DC bus, and the third DC bus.

[0158] Alternatively,​​​​Figure 11 The first sub-module and DC bus topology diagram provided by the embodiment of the application, the DC bus includes a first DC bus, a second DC bus and a third DC bus, as shown in Figure 11 The third DC bus is connected to the second DC bus through a second DC converter, the second DC bus is connected to an energy storage unit 210, and the energy storage unit 210 is connected to the first DC bus through a first DC converter; the first DC bus is connected to the DC side of the AC-DC conversion module to form a sub-module. After the AC sides of multiple sub-modules are connected in series, an inductor is connected in series, to form a bridge arm of a high-voltage cascaded grid energy storage converter, and the bridge arm can be connected to an AC bus through a star or double-star type.

[0159] Figure 12 The second sub-module and DC bus topology diagram provided by the embodiment of the application, referring to Figure 11 and Figure 12 Under the second topology, after the third DC bus is connected to the second DC bus through the second DC converter, the second DC buses between multiple sub-modules are connected in parallel, and the battery clusters of the energy storage unit 210 are connected to the first DC bus through an isolation type DC converter, the first DC bus is connected to the DC side of the AC-DC conversion module H-bridge to form a sub-module. In this embodiment, the first DC converter is an isolation type DC converter.

[0160] Figure 13 The third sub-module and DC bus topology diagram provided by the embodiment of the application, referring to Figure 11 and Figure 13 Under the third topology, the third DC buses between multiple sub-modules are connected in parallel, after the third DC bus is connected to the second DC bus through the isolation type DC converter, the battery clusters of the energy storage unit 210 are connected to the first DC bus through the first DC converter, and the first DC bus is connected to the DC side of the AC-DC conversion module H-bridge to form a sub-module. In this embodiment, the first DC converter is an isolation type DC converter.

[0161] Figure 14 The fourth sub-module and DC bus topology diagram provided by the embodiment of the application, referring to Figure 11 and Figure 14 Under the fourth topology, the third DC buses between multiple sub-modules are connected in parallel, after the third DC bus is connected to the second DC bus through the isolation type DC converter, the battery clusters of the energy storage unit 210 are connected to the first DC bus through the first DC converter, and the first DC bus is connected to the DC side of the AC-DC conversion module H-bridge to form a sub-module. In this embodiment, the second DC converter is an isolation type DC converter.

[0162] Figure 15For a topology diagram of the fifth seed module and DC bus provided in the embodiments of this application, see [link to relevant documentation]. Figure 11 and Figure 15 In the fifth topology, the third DC bus is connected to the second DC bus via a second DC converter, the battery clusters of the energy storage unit 210 are connected to the second DC bus, and different sub-modules in the same phase bridge arm are connected in series via the second DC bus; the battery clusters of the energy storage unit 210 are connected to the first DC bus via an isolated DC converter, and the first DC bus is connected to the DC side of the AC-DC conversion module H-bridge, forming a sub-module. In this embodiment, the first DC converter is an isolated DC converter.

[0163] Figure 16 For a topology diagram of the sixth seed module and DC bus provided in the embodiments of this application, see [link to relevant documentation]. Figure 11 and Figure 16 In the sixth topology, different sub-modules of the same phase bridge arm are connected in series via a third DC bus; the third DC bus is connected to the second DC bus via an isolated DC-DC converter; the battery clusters of the energy storage unit 210 are connected to the second DC bus, and the battery clusters of the energy storage unit 210 are connected to the first DC bus via a first DC-DC converter. The first DC bus is connected to the DC side of the AC-DC conversion module H-bridge, forming a sub-module. In this embodiment, the second DC-DC converter is an isolated DC-DC converter.

[0164] Figure 17 For a topology diagram of the seventh seed module and DC bus provided in the embodiments of this application, see [link to relevant documentation]. Figure 11 and Figure 17 In the seventh topology, different sub-modules of the same phase bridge arm are connected in series via a third DC bus; the third DC bus is connected to the second DC bus via a second DC converter; the battery clusters of the energy storage unit 210 are connected to the second DC bus, and the battery clusters of the energy storage unit 210 are connected to the first DC bus via an isolated DC converter. The first DC bus is connected to the DC side of the AC-DC conversion module H-bridge, forming a sub-module. In this embodiment, the first DC converter is an isolated DC converter.

[0165] This application also provides an energy storage power station, which includes the electrochemical energy storage system provided in any of the foregoing embodiments, and may also include power generation equipment, energy storage equipment, and power consumption equipment.

[0166] In addition to the energy storage system, an energy storage power station can also include a series of supporting facilities, such as monitoring and control systems and pairing systems, to achieve safe, efficient and stable operation.

[0167] Optionally, the energy storage station may include charging piles to charge electric vehicles.

[0168] For example,Figure 18 Another structural schematic diagram of the energy storage power station provided in the present application is shown in FIG. 2. As shown in FIG. 2, the energy storage power station includes an electrochemical energy storage system 20, and charging piles, electrolytic cells, energy storage devices, and power generation devices such as photovoltaic power generation devices, wind power generation devices, thermal power generation devices, hydroelectric power generation devices, and nuclear power generation devices. The electrochemical energy storage system 20, the photovoltaic / wind power generation devices, the thermal / hydroelectric / nuclear power generation devices, and the energy storage devices are connected to the power grid through a third AC bus, and are connected to local loads. The charging piles, the electrolytic cells, and other devices are connected to a direct current side network formed by the electrochemical energy storage system 20 and the like through a direct current line (a first DC bus, a second DC bus, or a third DC bus), and can work using direct current power in the system, such as charging the charging piles for electric vehicles, and using the electrolytic cells to electrolyze hydrogen. Figure 18 The energy storage power station system can convert clean solar energy and wind energy into electric energy using photovoltaic and wind power generation devices, and can provide stable and continuous electric power using thermal, hydroelectric, and nuclear power generation devices. The electric power can be transmitted to the power grid through the third AC bus to meet the daily power demand of the local loads and participate in the power allocation of the power grid. The electrochemical energy storage system 20 and the energy storage devices can store electric power when the electric power is in excess, and release electric power when the electric power is insufficient, thereby playing a role in peak shaving and valley filling and stabilizing power fluctuations.

[0169] The local loads can be any kind of loads, such as manufacturing equipment in a mechanical processing plant, refrigeration and heating equipment in an industrial park, and public facilities.

[0170] For the electrochemical energy storage system 20, the present application further provides a control method of the electrochemical energy storage system, which includes: controlling the first DC port OUT1 of the energy storage converter 220 to output a specified voltage; and electrically connecting the electrochemical energy storage system 20 to the power grid if the rotor speed of the synchronous condenser 230 matches the voltage frequency of the power grid, and the phase difference between the voltage phase of the AC bus and the voltage phase of the power grid is less than or equal to a preset value.

[0171] For the electrochemical energy storage system 20, the present application further provides a control method of the electrochemical energy storage system, which includes: detecting a voltage parameter of the power grid; the voltage parameter includes a voltage amplitude, a voltage frequency, and a voltage phase; controlling the first DC port OUT1 of the energy storage converter 220 to output a specified voltage; detecting a rotor speed of the synchronous condenser 230; detecting a phase difference between the voltage phase of the AC bus and the voltage phase of the power grid after the rotor speed matches the voltage frequency; and electrically connecting the AC bus to the power grid by closing the circuit breaker if the phase difference is less than or equal to a preset value.

[0172]

[0173] ​The first DC port OUT1 of the energy storage converter 220 outputs a specified voltage, so that the rotor speed of the synchronous generator 230 is slowly increased from 0 to a speed matching the voltage frequency of the power grid.

[0174] The preset value can be configured based on experience, for example, can be 5°, 3° or other values.

[0175] If the phase difference between the AC bus voltage and the grid voltage is large, i.e. greater than the preset value, the instantaneous voltages of the two will form a large difference. If the circuit breaker is closed at this time, a large current impulse will be generated in a short time, which may burn the equipment and even cause power grid fluctuations. Therefore, it is necessary to close all circuit breakers when the phase difference is less than or equal to the preset value, so as to completely integrate the electrochemical energy storage system 20 into the power grid. The electrochemical energy storage system 20 continuously and stably outputs AC voltage consistent with the amplitude, frequency and phase of the power grid until the power grid no longer needs the electrochemical energy storage system 20 to supply power, for example, receives a stop power supply instruction.

[0176] If the phase difference is greater than the preset value, the output voltage of the first DC port OUT1 of the energy storage converter 220 can be continuously adjusted to cause a small deviation between the voltage of the AC bus and the voltage frequency of the power grid, so as to realize dynamic calibration of the phase by using the correlation between the frequency and the phase.

[0177] Optionally, the control method further includes: if the phase difference is greater than the preset value, adjusting the output voltage of the first DC port OUT1 of the energy storage converter 220 to control the voltage frequency of the AC bus to deviate from the voltage frequency of the power grid, so as to correct the phase difference.

[0178] The electrochemical energy storage system 20 further includes first to fourth circuit breakers, the first and second circuit breakers are respectively connected in series between the AC bus and the two ends of the first transformer T1, and the third and fourth circuit breakers are respectively connected between the synchronous generator 230 and the two ends of the second transformer T2. For the electrochemical energy storage system 20, the main flow of the foregoing control method is described in detail with reference to Figure 19 , wherein the first circuit breaker is located between the energy storage converter 220 and the first transformer T1, and the fourth circuit breaker is located between the synchronous generator 230 and the second transformer T2.

[0179] Figure 19 The flowchart of the control method of the electrochemical energy storage system provided in the present application is applied to the electrochemical energy storage system 20, as shown in Figure 19 , the method includes:

[0180] In step S101, the second circuit breaker and the third circuit breaker are closed, so that the grid voltage is transmitted to the detection module through the AC bus and the first transformer T1, and the amplitude, phase and frequency of the grid voltage are detected by the detection module.

[0181] Step S102, control the first DC port OUT1 of the energy storage converter 220 to output a specified voltage;

[0182] Step S103, start the energy storage converter 220, detect the rotor speed of the synchronous condenser 230, control the voltage frequency of the AC port OUT3 so that the rotor speed of the synchronous condenser 230 slowly changes from 0 to match the grid frequency; after the rotor speed of the synchronous condenser 230 matches the grid frequency, proceed to step S104;

[0183] Step S104, detect the phase difference between the voltage phase of the AC bus and the grid; if the phase difference is greater than a preset value, execute step S105; if the phase difference is less than or equal to the preset value, execute step S106;

[0184] Step S105, control a slight deviation between the AC bus voltage frequency and the grid frequency; return to step S104.

[0185] Step S106, close the first circuit breaker and the fourth circuit breaker to connect the energy storage converter 220 to the AC bus through the first transformer T1 and connect the synchronous generator 230 to the AC bus through the second transformer T2, realize formal grid connection of the electrochemical energy storage system 20 and the grid, and enable the system to stably deliver power to the grid;

[0186] Step S107, continuously output AC voltage consistent with the grid voltage amplitude, frequency, and phase until a stop power supply instruction is received.

[0187] The stop power supply instruction can be issued artificially or by a grid-side device. When the grid-side device detects that the power demand is low, it can issue the instruction to the electrochemical energy storage system 20.

[0188] Through the synergistic effect of the synchronous condenser 230 and the high-voltage cascaded energy storage converter (i.e., the energy storage converter 220), multi-dimensional complementary advantages are achieved: the synchronous condenser 230 can respond instantaneously to sudden disturbances in the grid and provide instantaneous active power support due to its physical inertia characteristics, while the energy storage converter 220 releases or absorbs active power within a millisecond time scale through virtual inertia control technology, enhancing the equivalent inertia of the system. Together, they build a multi-time scale frequency support system. At the same time, the synchronous condenser 230 has a large current-carrying capacity and can effectively deal with short-circuit faults. In addition, the synchronous condenser 230 can provide low-frequency damping, and the high-voltage cascaded energy storage converter can provide medium-high frequency active damping, which, in combination, effectively suppresses wideband oscillation. In the system design, the synchronous condenser 230 is responsible for dynamic reactive power regulation, and the high-voltage cascaded energy storage converter realizes active-reactive power collaborative control through precise control of active power output.

[0189] In particular, the dynamic voltage regulation function of the high-voltage cascaded energy storage converter on the DC side can be directly used for the excitation of the synchronous compensator 230, breaking through the clamping limit of the DC side battery voltage of the traditional topology, so that the excitation DC voltage can be dynamically optimized according to the grid state, thereby improving the reactive power regulation accuracy and response speed of the synchronous compensator 230.

[0190] For the electrochemical energy storage system 20, the embodiment of the present application further provides a control device of an electrochemical energy storage system, comprising: a voltage detection module configured to detect a voltage parameter of a power grid; the voltage parameter comprises a voltage amplitude, a voltage frequency and a voltage phase; a voltage output module configured to control a first DC port OUT1 of an energy storage converter 220 to output a specified voltage; a rotating speed detection module configured to detect a rotor rotating speed of a synchronous compensator 230; a phase difference detection module configured to detect a phase difference between the voltage phase of an AC bus and the voltage phase of the power grid after the rotor rotating speed matches the voltage frequency; and a grid connection module configured to close a circuit breaker to realize electrical connection between the AC bus and the power grid if the phase difference is less than or equal to a preset value.

[0191] Optionally, the control device further comprises a phase difference correction module configured to: if the phase difference is greater than the preset value, adjust the output voltage of the first DC port OUT1 of the energy storage converter 220 to control the voltage frequency of the AC bus to deviate from the voltage frequency of the power grid, so as to correct the phase difference.

[0192] The control device provided by the embodiment can execute the method provided by the method embodiment, and has similar implementation principles and technical effects, which will not be described here in detail.

[0193] The embodiment of the present application further provides an electronic device, which comprises at least one processor and a memory.

[0194] Optionally, the device further comprises a communication component. The processor, the memory and the communication component are connected through a bus.

[0195] In the specific implementation process, the at least one processor executes the computer execution instructions stored in the memory, so that the at least one processor executes the above-mentioned method.

[0196] The specific implementation process of the processor can refer to the method embodiment, and has similar implementation principles and technical effects, which will not be described here in detail.

[0197] In the above embodiments, it should be understood that the processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor. The steps of the method disclosed in combination with the application can be directly embodied as hardware processor execution, or executed by a combination of hardware and software modules in the processor.

[0198] The memory can include a random access memory (RAM), and can also include a non-volatile memory (NVM), such as at least one disk memory.

[0199] The bus can be an industry standard architecture (ISA) bus, a peripheral component (PCI) bus, or an extended industry standard architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of the present application does not limit to only one bus or one type of bus.

[0200] The present application also provides a computer program product, comprising a computer program, which, when executed by a processor, implements the above method.

[0201] The present application also provides a computer readable storage medium, which stores computer execution instructions, and when a processor executes the computer execution instructions, the above method is implemented.

[0202] The above readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The readable storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0203] An example readable storage medium is coupled to the processor such that the processor can read information from the readable storage medium and can write information to the readable storage medium. Of course, the readable storage medium can also be a part of the processor. The processor and the readable storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the readable storage medium can also exist as discrete components in the device.

[0204] The division of units is only a logical functional division, and in actual implementation, there can be another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0205] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0206] In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit.

[0207] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application or the part of the present application that essentially contributes to the prior art or the part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method of each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various program code storage media.

[0208] Those skilled in the art can understand that all or part of the steps of the above-mentioned method embodiments can be completed by program instruction related hardware. The foregoing program can be stored in a computer readable storage medium. The program executes to perform the steps of the above-mentioned method embodiments; and the foregoing storage medium includes various media capable of storing program codes, such as ROM, RAM, magnetic disk, or optical disk.

[0209] Finally, it should be noted that other embodiments of the present application will readily occur to those skilled in the art upon consideration of the specification and practice of the present application disclosed herein. The present application is intended to include all such variations, uses, or adaptations of the application in which the general principles of the application are used to best advantage and encompassed within its scope. The present application is not limited to the precise structures described and shown in the accompanying drawings and figures, and can be practiced with variation of modifications and alterations without departing from the scope of the present application. The scope of the present application is limited only by the claims appended hereto.

Claims

1. An electrochemical energy storage system, characterized by, The energy storage system comprises: an energy storage unit, an energy storage converter and a synchronous compensator; an AC port of the energy storage converter is connected to an AC bus in parallel with a stator AC port of the synchronous compensator, and the AC bus is configured to be connected to a power grid; a first DC port of the energy storage converter is electrically connected to a rotor excitation port of the synchronous compensator to perform excitation; a second DC port of the energy storage converter is electrically connected to the energy storage unit to realize charging and discharging of the energy storage unit.

2. The system of claim 1, wherein, The energy storage converter is further configured to: calculate an output voltage of the first DC port based on a frequency fluctuation parameter of the power grid; and / or calculate a target excitation voltage of the synchronous compensator based on a voltage fault parameter of the power grid, and adjust the output voltage of the first DC port according to the target excitation voltage.

3. The system of claim 1, wherein, Each phase bridge arm of the energy storage converter adopts a cascade topology of a plurality of sub-modules, AC sides of the plurality of sub-modules are connected in series, and DC sides are connected to the energy storage unit.

4. The system of claim 3, wherein, The energy storage converter bridge arm adopts star or double-star connection.

5. The system of claim 3, wherein, The sub-module comprises an AC-DC conversion module, a first DC converter and a second DC converter connected in sequence.

6. The system of claim 5, wherein, The first DC converter and / or the second DC converter is an isolated DC converter.

7. The system of claim 5, wherein, Further comprising a first DC bus, a second DC bus and a third DC bus; the third DC bus is connected to the second DC bus through the second DC converter, the second DC bus is connected to the energy storage unit, the energy storage unit is connected to the first DC bus through the first DC converter; the first DC bus is connected to the DC side of the AC-DC conversion module.

8. The system of claim 7, wherein, The energy storage converter bridge arm adopts double-star connection to form a modular multilevel converter DC bus; The modular multilevel converter DC bus selectively has a connected sub-module string, and the sub-module string is composed of a plurality of the sub-modules connected in series.

9. The system of claim 7, wherein, The second DC bus among the plurality of sub-modules in each phase bridge arm is connected in parallel.

10. The system of claim 7, wherein, The third DC bus among the plurality of sub-modules in each phase bridge arm is connected in parallel.

11. The system of claim 7, wherein, The plurality of sub-modules in each phase bridge arm are connected in series through the second DC bus.

12. The system of claim 7, wherein, The plurality of sub-modules in each phase bridge arm are connected in series through the third DC bus.

13. The system of any of claims 1-12, wherein, The AC output end of the energy storage converter is connected to the AC bus through a first step-up transformer, and the stator AC port of the synchronous compensator is connected to the AC bus through a second step-up transformer; or The AC output end of the energy storage converter is connected to the AC bus through a step-up transformer in parallel with the stator AC port of the synchronous compensator.

14. An energy storage power plant characterized by, The energy storage system comprises: a charging pile and the electrochemical energy storage system of any one of claims 1-13.

15. A method of controlling an electrochemical energy storage system, characterized by, The method is applied to the electrochemical energy storage system of any one of claims 1-13, and the method comprises: controlling the first DC port of the energy storage converter to output a specified voltage; if the rotor speed of the synchronous compensator matches the voltage frequency of the power grid, and the phase difference between the voltage phase of the AC bus and the voltage phase of the power grid is less than or equal to a preset value, then electrically connecting the electrochemical energy storage system to the power grid.

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